Gaseous fuel powered engines are common in many applications. For example, the engine of a locomotive can be powered by natural gas (or another gaseous fuel) alone or in combination with another liquid or gaseous fuel (e.g., diesel fuel). Natural gas may be more abundant and, therefore, less expensive than other liquid fuels. In addition, natural gas may burn cleaner in some applications, and produce less greenhouse gas.
Natural gas, when used in a mobile application, may be stored in a liquid state onboard the associated machine. This may require the natural gas to be stored at cold temperatures, typically about −100 to −162° C. The liquefied natural gas is then drawn from the tank by gravity and/or by a boost pump, and directed to a high-pressure pump. The high-pressure pump further increases a pressure of the fuel and directs the fuel to the machine's engine. In some applications, the liquid fuel may be gasified prior to injection into the engine and/or used in conjunction with diesel fuel (or another fuel) before combustion.
An exemplary fuel system used to pump cryogenic fluids is disclosed in U.S. Patent Application Publication No. 2013/0283824 (the '824 publication) of Madison that published on Oct. 31, 2013. In particular, the '824 publication discloses a configuration of cryogenic pumps used to pump LNG. A single liquid vessel is provided, and two electrically driven centrifugal-type pumps are disposed in series with each other, inside of vessel. Each pump is provided with its own shaft, and the two pumps are operated at different speeds. A lower of the two pumps in the vessel draws in fluid directly from the vessel, and discharges the fluid to an intake of an upper of the two pumps. A high-pressure liquid inlet provides fluid to the vessel, and a two-phase outlet is connected to the upper pump. The pumps hang from a top support plate surrounding the vessel.
While the pump configuration of the '824 publication may be acceptable in some applications, it could have limited applicability. In particular, centrifugal type pumps may not be capable of generating pressures high enough for some applications. In addition, it may be difficult in some applications to supply each of the pumps with electrical power and to separately control the speeds of the pumps. Further, drawing fluid directly from the tank may allow for contamination and/or damage of the pumps.
The disclosed fuel system is directed to overcoming one or more of the problems set forth above.